Does a lighting dimmer draw more current from the line when dimmed down lower than 100%?

Question

I'm just curious as to how this all works. If I have a lighting fixture on a circuit, and I hook up a Radio Shack X10 dimmer module to it, WHEN it's anything BELOW 100% does that draw more current from that circuit?

Answer 1

No, it draws less. It is proportionately less depending on how much lower you set it.

BTW, the X10 system is not unique to any one company, they are universal. Any X10 module should work with any X10 system.

Another way to save energy is a Compact Florescent bulb. They look similar to a regular bulb, but they are florescent. They use much less power.

They might not be compatible to a dimmer, though. Since they use so much less power, the cost savings of the dimmer is moot.

Answer 2

Short Answer:
No
Long Answer:
It's an interesting question because as you may know, metal has a higher resistance when its hot (ie it is more difficult for electrons that make up the electric current to flow through the metal when the metal is hot. The filament in an incandescent lamp is made of tungsten metal and is at a temperature of approx 3000 degrees C when lit.
BUT.. even though this is the case, when you decrease the voltage across the tungsten (by lowering the brightness setting on the dimmer) the current drops. A light bulb is non ohmic which means that although as voltage increases, current increases they do not increase in direct proportion (so the bulb does not obey Ohm's law) but the light bulb still has a positive resistance (compared to a device which has a negative resistance such as a tunnel diode which is a semiconductor and over a certain voltage range, as the voltage across the diode increases, the current actually decreases!! THIS IS NOT THE CASE WITH A BULB)
I prefer to think about a lamp dimmer in terms of energy. When a bulb is connected to the mains, current flows through the lamp and in doing so, the electrons give up energy to the filament and this energy is given out as light. Energy used up per second (Power) = Voltage x Current.
A lamp dimmer is used to reduce the amount of energy that reaches the bulb, an old type of dimmer used a variable resistor which was wired in series with the bulb limiting the current so less energy was dissipated per second, however the resistor itself had to dissipate energy and used to get very hot and needed to be large to dissipate this heat.
Modern dimmers like your one use a device called a "triac" which is a semiconductor and switches the current to the light bulb on and off very fast or in technical terms it alters the duty cycle (duty cycle is the ratio of the time that the bulb is on to the time that the bulb is off). The higher the duty cycle the more energy is delivered to the bulb per second and by turning the brightness on the dimmer down, you decrease the duty cycle so less energy is transferred and the bulb is dimmer but you don't waste power in a resistor.
A point about energy saving compact fluorescent lamps:
They are not compatible with a dimmer switch designed for use with a standard filament bulb. A fluorescent tube requires control electronics to regulate the tube (older ceiling fluorescent tubes had a magnetic ballast to control the current flow through the tube) and these will not work with or may be damaged by a standard dimmer due to the sharp variations in current produced by the switching action of the triac.

Answer 3

amperage(current) is inversely proportional to voltage. it's called the PIE formula in electricity. look it up.